Methods and apparatus for decontaminating enclosed spaces

ABSTRACT

A portable apparatus for decontaminating an enclosed room or other space includes a passageway having an air inlet at one end and an outlet at the other end. A pump causes a flow of air through the passageway from the inlet to the outlet. A heater heats the air flowing through the passageway to a predetermined temperature, a evaporator being in communication with the passageway. Liquid decontaminant is pumped from a supply of decontaminant to the evaporator to be evaporated and for the evaporant to be delivered to the air flow in the passage to flow in the air flow from the outlet to the rooms to be decontaminated. A universally rotating nozzle is provided at the outlet to distribute the decontaminant containing air throughout the enclosure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/509,192 filed Sep. 24, 2004, which is a U.S. nationalization of PCTApplication No. PCT/GB03/01386, filed Mar. 28, 2003, which claimspriority to United Kingdom Application Nos. 0207452.4, filed Mar. 28,2002 and 0211851.1, filed May 22, 2002, the disclosure of which areincorporated herein by specific reference.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

This invention relates to methods and apparatus for decontaminatingenclosed spaces such as hospital wards and clean rooms in which amanufacturing or other processes take place in sterile conditions.

2. The Relevant Technology

Vaporized aqueous solution of hydrogen peroxide has been used todecontaminate the internal surfaces of enclosures used for asepticprocessing in the pharmaceutical industry since about 1990, but it hasalways been difficult to use the same technology to decontaminate largerenclosed volumes such as rooms.

The conventional apparatus for decontaminating enclosures comprises agas generator in a closed circuit including the enclosure such asdescribed in U.S. Pat. No. 5,173,258. In this design the hydrogenperoxide and water vapors are produced by flash evaporation of anaqueous solution into a heated air stream, which then carried the gas tothe space to be decontaminated. The air and mixture of gases then mixeswith the air inside the chamber before being returned to the gasgenerator, where the gas is decomposed, dried, heated and more liquid isflash evaporated and the air mixture is returned to the chamber.

The processes performed on the returned gas are complex, and include thesteps of decomposing the gas, drying and re-heating. This completeprocess was considered necessary because it was understood that thehydrogen peroxide gas decomposed according to a half-life rule and henceto maintain an adequate concentration inside the chamber a circulatingsystem that decomposed the gas was thought to be necessary.

Recent work by Watling, ISPE Conference Zurich, September 1999 has shownthat the gas does not decompose but is stable. It is therefore notnecessary to remove the returning gas from the chamber.

S. S. Block reports in the 5th Edition of Disinfection, Sterilizationand Preservation page 189 that a 3% hydrogen peroxide aqueous solutiongives a log 8 reduction of Staphylococcus aureus in under 20 minutes. Aslower rate of deactivation has been found in experimental work whenexposing Staphylococcus aureus to gas generated from 35% solution, whenthe process was operated at a temperature below the dew point thuscausing condensation. Under these gassing conditions the first dropletsof dew form on the organism at a much higher concentration than that ofthe original liquid, typically about 65% w/w, the exact value dependingon the moisture content of the carrier gas.

As stated above, in the conventional system the air in the chamber to bedecontaminated is dried prior to injecting the decontaminating gas. Thisis done either to allow a high level of gas concentration to be achievedbefore the onset of condensation, or to operate the process avoidingcondensation maintaining the gas in a dry state. The vapor pressureequations for hydrogen peroxide and water may be used to calculate theconcentration of the hydrogen peroxide and water vapor that will causecondensation and hence may be used either to avoid the conditions thatwill cause the onset of condensation or to calculate the concentrationof any condensate that may be formed as a result of passing the flashevaporated vapors into the sealed enclosure. If the RH in the chamber ishigh the condensation will form quickly but as a relatively weaksolution. Evaporating 35% w/w hydrogen peroxide into a chamber at 20° C.and 85% RH will cause the condensate to form at in excess of 6% w/w,although the concentration of the vapor will be about 120 ppm. It iswell known that 6% hydrogen peroxide is active against microorganismsand will cause bio-deactivation of surfaces. If it is intended tooperate a process where condensation is formed it is therefore notnecessary to reduce the humidity in the chamber under normal operatingconditions as the RH will be less than 85% and hence the condensationwill form at a concentration greater than 6%. The same is not true whenoperating a process that is intended to avoid condensation, in such aprocess it is essential to ensure that the moisture content of the airinside the enclosed space at the start of the process is low.

It is believed that the difference between the liquid process asreported by Block and a gaseous dew process is the rate of delivery ofthe hydrogen peroxide condensation. It follows that using a standardrecirculating gas generator placed outside the space to bebio-decontaminated; there may not be an adequate evaporation capacity toachieve a sufficiently high condensation rate to deactivate the organisminside the chamber. The deactivation process may be enhanced by the useof mixtures of chemicals but the principal of the rate of delivery stillremains. Whilst for a dry gas process the rate of delivery of hydrogenperoxide and water vapor are not so critical it is still important toevaporate the liquid as fast as is practical as this will shorten thetime required to raise the gas concentration and achieve a satisfactorybio-decontamination.

An analysis of the equations governing the vapor pressure of water andhydrogen peroxide by Watling et al and published in the PDA Journal ofScience and Technology November/December 2002 vol 56, No 6 291-299,shows that the gas concentration inside a chamber may be raised to thedew point by passing flash evaporated vapor into the sealed enclosure,but as soon as the dew point is reached condensation will form at ahigher concentration than the evaporated liquid thus reducing the gasconcentration. The gas concentration will continue to fall as moreliquid is evaporated until the equilibrium vapor pressure for theevaporated liquid is reached at the temperature of the chamber.

There are two views about the mechanisms involved in thebio-decontamination using hydrogen peroxide and water vapor. The firstis that it is important to ensure that the gas remains in the dry stateand the second that condensation is essential. It has been wellestablished that dry hydrogen peroxide gas at elevated temperatures willbio-deactivate micro-organisms, and the same dry process has been shownto work at room temperatures. The condensation process in which the gasconcentration is raised to the dew point and condensation is allowed toform appears to be faster at room temperatures.

SUMMARY OF THE INVENTION

The apparatus and method described in the present invention will workequally well with both the dry and condensation processes. Whenoperating a dry process it is essential to monitor the water andhydrogen peroxide concentration in the gaseous phase to ensure that theyremain below the saturated vapor concentrations. When operating acondensation process it is helpful to have an indication of the pointduring the cycle when condensation starts to form and the subsequentrate of formation. A technique and apparatus to make such a measurementof condensation is described patent application UK 0291983.1

An ideal bio-decontamination cycle is in three phases. The first phaseis to bring all of the equipment to thermal stability but may also beused to adjust the relative humidity in the chamber to a pre-set level,the second is used to raise the gas concentration to the required leveland maintain that concentration for a sufficient length of time toachieve the required level of bio-decontamination, and the third andlast phase to reduce the concentration of the sterilant in the enclosedspace to a predetermined value.

U.S. Pat. No. 4,863,688 discloses a method of selectively destroyingorganisms within a chamber such as an incubator comprising the steps ofintroducing vapor phase hydrogen peroxide into the chamber at a ratesufficient to cause a predetermined concentration of hydrogen peroxideto be reached while preventing a substantial change in pressure orcondensation of the hydrogen peroxide in the chamber. When thepredetermined period of time has elapsed, the vapor phase hydrogenperoxide is removed from the chamber. In a preferred embodimentdisclosed an incubator is provided with a separate apparatus forproducing a flow or air containing hydrogen peroxide vapor which isdelivered to the incubator. Alternatively the apparatus for producingthe air flow containing hydrogen peroxide vapor may be built into theincubator.

RU-C-2054295 discloses a device for sanitary treatment of air for use inlivestock and poultry facilities and in various branches of industryincluding biological, food, light industry, chemical, coal, constructionand other applications. The device includes a housing with an inlet andan outlet, a heating element, disinfected evaporator in the form of aperforated header closed at one end and enclosed in a porous sheath, theheader is installed along the housing axis. The device has a reservoircontaining disinfectant solution secured to the housing and connected tothe open end of the evaporator. The tubular evaporator is arranged inthe porous sheath along a spiral line and the heating element is mountedwithin the centre of the spiral.

This invention provides a method of decontaminating an enclosed spacecomprising the steps of providing an aqueous solution of hydrogenperoxide in the enclosed space, producing hydrogen peroxide/water vaporfrom said aqueous solution, creating an air stream in the enclosedspace, introducing hydrogen peroxide/water vapor into the air stream,distributing the hydrogen peroxide/water vapor containing air streamthroughout the space to be decontaminated and then removing the hydrogenperoxide/water vapor from the space; characterized in that the airstream is heated before hydrogen peroxide/water vapor is introduced toit, the hydrogen peroxide/water vapor is flash evaporated from anaqueous solution of hydrogen peroxide/water vapor from said supply intothe air stream, and the air stream carrying the flash evaporatedhydrogen peroxide/water vapor is distributed throughout the enclosedspace to achieve bio-decontamination of the enclosed space.

By placing the gas generator inside the room and simply heating thecarrier gas and then evaporating this sterilant into the air stream itis possible to use the available energy much more efficiently. Theincrease in efficiency is derived from the removal of the system fordecomposing and drying the carrier gas, and also because there is noneed for any pipe work to transport the carrier gas and decontaminantfrom an external generator.

This increased efficiency provides more energy for the primary functionof heating the carrier gas and flash evaporating the liquid. Theefficiency increase is so great as it allows a trebling of the rate offlash evaporation from the same energy source and hence the rate ofincrease in the gas concentration or the achievable rate of formation ofcondensation once the dew point has been reached is also trebled.

The simplified design is also much smaller and lighter than aconventional gas generator and hence considerably less expensive tomanufacture. It is therefore realistic to place a number of such devicesinside a sealed enclosure to be decontaminated. This reduction in sizeand weight makes the apparatus portable and hence makes it practical touse the same apparatus to bio-decontaminate a number of facilitieseither on the one site or at different locations. As stated above it isimportant to make measurements of the hydrogen peroxide and water vaporconcentrations.

To satisfy this requirement an instrument module that is placed insidethe enclosed space has been devised that will also link back to thecontrol system that is external to the enclosed space. Provision hasbeen made within the control systems both at the gas generator (s) andthe instrument module to connect a number of condensation sensors sothat the process may be operated either as a dry gas or as a saturatedvapor process Each simplified generator will have its own controlsystem, which is linked to a control box external to the room andconnected by a single control cable. By using a central control system,such as a laptop computer, it is possible to control a number ofgenerators that are linked together from outside the enclosed space.With the present arrangement it is possible to control eight generatorsfrom a single laptop, should a larger number be required a secondcomputer would be needed. It is also possible to control multipleaeration units and dehumidifiers from the same laptop computer.

Because the apparatus is portable and may therefore be used at differentsites in order to ensure that the apparatus does not carry contaminationfrom one location to another it is essential that all of the externaland internal surfaces are bio-decontaminated during the gassing cycle.To achieve this objective components have been mounted in such a way toensure that they are exposed to the sterilizing gas. The tubular steelframe has been sealed and the control box is purged with the sterilizinggas drawn from the room. Tests have been performed to check thatfollowing a bio-decontamination cycle all of the surfaces of theapparatus have been rendered safe.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention will now be discussed withreference to the appended drawings. It is appreciated that thesedrawings depict only typical embodiments of the invention and aretherefore not to be considered limiting of its scope.

FIG. 1 is a wholly diagrammatic view of an apparatus for generating anddelivering an air flow containing an evaporated decontaminant to anenclosed space;

FIG. 2 is a similar view to FIG. 1 showing the components of theapparatus including the evaporator, liquid sterilant supply and outletnozzle in greater detail;

FIG. 3 is a perspective view of a portable unit embodying the apparatusof FIGS. 1 and 2;

FIG. 4 in an exploded view of the unit of FIG. 3;

FIG. 5 is a plan view of the evaporator;

FIG. 6 is a cross-sectional view on the line 6-6 of FIG. 5;

FIG. 7 is a cross-sectional view of an alternative form of evaporator;

FIG. 8 is a perspective view of a control box for the apparatus of FIGS.3 and 4 with a lid of the box shown open;

FIG. 9 is an exploded view of a monitoring unit for use in conjunctionwith the apparatus of FIGS. 3 and 4; and

FIGS. 10 and 11 show further embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The gas generator apparatus will be described firstly with reference toFIGS. 1 and 2. Room air, which may or may not already contain previouslysupplied hydrogen peroxide and water vapor, is drawn into an inletconduit 10 through a HEPA filter 11 by a variable speed motor driven fan12. The HEPA filter 11 removes any particles from the air stream toensure that the delivered air is of the correct quality when thegenerator is used in a clean room. The conduit delivers the air to aheater 13 where the temperature is raised to a predetermined level asdescribed below.

The heated air then passes into an evaporator 14 where a liquidsterilant comprising aqueous hydrogen peroxide is flash evaporated. Byway of example, the sterilant may comprise an aqueous solutioncontaining 30 to 35% hydrogen peroxide. If the sterilent includesperacetic acid, the proportion of hydrogen peroxide can be reduced to15% with 0.5% peracetic acid and a balance of water. In practice theheater 13 and the evaporator 14 are combined in a single unit as shownin FIGS. 2 to 7 to which reference will be made later. The physicalshape and dimensions of the combined heater/evaporator are designed tocontrol the energy balance between that used to heat the carrier gas andthat used for flash evaporation.

A supply of aqueous hydrogen peroxide liquid is stored in a container 15and is pumped to the evaporator 14 by a liquid pump 16. The carrier gasand vapors are delivered from the evaporator through a conduit 17 to adistribution nozzle 18 for delivery of the sterilant vapor to the spaceto be decontaminated. The liquid container is demountable from the frame19 to reduce the weight of the unit and make it more easily handcarried.

FIGS. 3 and 4 show a practical embodiment in which the gas generatorapparatus is supported in an tubular steel framework 19 for ease ofmovement. The apparatus is light enough to be carried by the user and ascan be seen in FIG. 4 can have caster wheels 20 to enable it to beeasily maneuvered into position.

The tubular framework is sealed to prevent any contamination beingintroduced to the enclosure by the frame. Ideally, the apparatus shouldnot be placed inside a housing unit. Any covering of the apparatus wouldrestrict the sterilant gas movements around and through the apparatus,which is essential to ensure that the apparatus itself is also surfacedecontaminated because otherwise it may contaminate the area in which itis placed. FIGS. 3 and 4 also show the enclosed control box 70 for theapparatus which will be described in greater detail below.

FIG. 3 shows the outlet nozzle in greater detail. The nozzle has amotorized power unit 18 a which rotates the nozzle assembly about avertical axis. The nozzle assembly includes a laterally extending arm 18b having an enclosed drive for rotating the nozzle tip 18 c about ahorizontal axis to provide a universal discharge of heated air/hydrogenperoxide sterilant vapor around the room or other enclosure. The motorand nozzle assembly are formed as a unit and may be detached at thecoupling 18 d shown in FIG. 4 from the outlet of the evaporator anddismounted from the frame to be transported independently of the gasgenerator unit.

Multiple units may be provided as necessary and separate fan units mayalso be provided to circulate the sterilant atmosphere throughout theroom or enclosure.

An ideal decontamination cycle may have three distinct phases. In thefirst optional phase, the relative humidity in the room or otherenclosure is adjusted to a pre-set level. In the second phase the gasconcentration of sterilant gas is raised to form a required layer ofcondensation over all surfaces in the enclosure for a sufficient lengthof time to achieve the required level of decontamination. In the thirdand last phase the sterilant is removed from the enclosure. This isachieved using the room aerator system described and illustrated inInternational Patent Publication No. WO 02/11864.

If a HVAC system is available for the room or enclosure then this may beused to achieve the required level of relative humidity at the start ofthe process, and if the HVAC exhausts to a safe area to remove thesterilant at the end. Alternatively a portable dehumidifier may be usedto adjust the initial relative humidity and a catalytic scrubber used tocirculate the gas to remove the sterilant.

In the decontamination cycle referred to above the initial phase oftreatment in the adjustment of the relative humidity in the room orchamber may be omitted and the process commenced at the currentprevailing conditions in the enclosure since the relative humidity inthe enclosure would normally be well below dew point and so aconsiderable amount of sterilant/water vapor would need to be generatedin the enclosure before condensation would occur.

Reference is now made to FIGS. 5 and 6 which illustrate the combinedheater/evaporator 14/15 in greater detail. The heater/evaporatorcomprises a cast cylindrical aluminum block 30 which is mountedframework 19 with the axis of the block extending vertically. The lowerend of the block has a shallow cylindrical recess 31 and a circular baseplate 32 is attached to the periphery of the block extending across therecess by screws (not shown) the base plate 32 has a central aperture 33in which the end of the inlet conduit 10 is mounted to deliver a supplyof air to the recess in the block.

The upper end of the block also has a cylindrical recess 34 and acentral top plate 35 is mounted on the periphery of the block over therecess by set screws 36. The top plate 35 has a central aperture 39 inwhich an outlet conduit 40 from the block is mounted.

The block is formed with a central cylindrical cavity 37 extending intothe block from the upper end thereof in which the outlet conduit 40extends stopping short of the bottom of the cavity. The block 30 has amultiplicity of axially extending passageways 38 adjacent the outersurface of the block and spaced around the block leading from the lowerrecess 31 and the block upper recess 34 for flow of air from the bottomrecess to the top recess from where the air can flow into the cavity 37and thence into the outlet conduit 40. The liquid sterilant from thestorage container 15 is delivered via one or more inlet conduits 41providing injection points which extend through the top plate 35adjacent to the outlet conduit 40. The conduits 41 lead into the cavity37 in the block but stop short of the bottom of the cavity. A secondinlet conduit 41 is shown and preferably three such conduits areprovided at spaced locations around the outlet conduit.

The body 30 is encircled by a cylindrical jacket in which an electricalresistance heater 42 is mounted for heating the body 30 to a requisitetemperature to pre-heat the airflow through the block and also to ensurethat sterilant delivered by the conduit 41 to the bottom of the cavity37 of the block is flash evaporated from the bottom of the cavity toproduce a vapor which is entrained in the flow of air through the flowof heated air through the outlet conduit 40 for delivery into the roomto be sterilized.

The heating unit of the heater-evaporator is coupled to the control unitto the apparatus and a temperature probe 44 is mounted in a radialdrilling 45 in the body 30 below the cavity 37 to measure thetemperature of the body for adjusting, through the control unit, thepower supply to the resistance heating element to enable the body to bemaintained at a requisite temperature for pre-heating the air flowingthrough the body and flash evaporating the sterilant delivered to thebody.

FIG. 7 of the drawings shows an alternative form of heater 13 in whichthe outlet from the fan 12 is coupled to an inlet 50 to a lower chamber51 containing an electrically powered air heater 52. At the upper end ofthe chamber 51 there is an annular evaporator block 53 having a centralport 54 for gas flow and an evaporator plate 55 is located on top of theblock. The block has a spirally wound heating element 56 embeddedadjacent the surface of the block. Thus the heater 52 can be used toraise the temperature of the air flowing through the device to one leveland the second heater 56 can be used to maintain the surface of theevaporator plate at the requisite temperature for flash evaporation ofan aqueous solution of hydrogen peroxide.

The heater has an upper chamber 57 in which an outlet conduit 58 ismounted having ports 59 spaced around the conduit through which air canenter the conduit from the upper chamber as indicated by the arrows. Thelower end of the conduit is closed by an air deflector 61 whichpartially overlies the evaporation plate and causes the air flowemerging from the port 54 in the evaporator heater to disperse outwardlyover the evaporator plate before flowing upwardly and hence through theport 59 into the inlet conduit. Delivery tubes for aqueous hydrogenperoxide extend downwardly through the upper chamber 57 to stop justshort of the surface of the evaporation plate to drip aqueous hydrogenperoxide onto the plate which flash evaporates and is entrained in theair flow over the plate which passes upwardly into the outlet conduit58. The arrangement is otherwise similar to that of FIGS. 3 and 4.

Reference is now made to FIG. 8 of the drawings which shows the controlbox of the gas generator of FIGS. 3 and 4 in greater detail. The controlbox comprises a casing 70 having a lid 71 shown in the open position inFIG. 8. The fan 11 which is of the centrifugal type is mounted in theupper end of the box and has an upwardly facing mounting plate 72 formedwith an outlet port 73 to receive the evaporator 13,14 with the inlet tothe evaporator in communication with the port 73.

A liquid pump 74 is mounted on one side of the box powered by anelectric motor for delivering aqueous hydrogen peroxide to theevaporator. A mains cable connection for the unit for the various motorsand other devices requiring power supply is indicated at 75. The cablealso provides couplings to the controllers 76 for the unit which aremounted on the inside of the lid 71.

To ensure that contamination does not reach the enclosure from theinterior of the control box for the gas generator, a fan 77 is mountedon one side of the control box to deliver air carrying sterilant fromthe surrounding atmosphere in the enclosure through the control box tosterilize the interior surfaces of the control box.

Reference is now made to FIG. 9 of the drawings which shows in explodedform a monitoring unit for monitoring air temperature, gas concentrationand humidity in the enclosure. The monitoring unit comprises a box 80 toreceive the monitoring equipment and mounted on wheels 81 to enable thebox to be readily maneuvered around the enclosure and also moved fromside to side where it is to be used. The box has a lid 82 formed withinlet and outlet ports 83,84 respectively. The inlet port has a motordriven fan 85 disposed below the port to draw in air from the enclosurecontaining the dispersed sterilant to cause an air flow through theelements in the box to sterilize the interior surfaces of the box andthereby to ensure that the room or other enclosure is not contaminatedby anything within the interior of the box.

The apparatus described particularly with reference to FIGS. 3 to 9 isintended to be readily portable or transportable from room to room whereit is to be used. It provides a source of heated air carrying hydrogenperoxide vapor sterilant directly into the room and distributes the airflow throughout the room until condensation occurs on all surfaceswithin the room. No external pipework connections are required to passthrough walls of the room just power supply and control cables for theapparatus. No special installation requirements arise as in conventionalgas generator circuit systems as referred to earlier.

Thus each of the components of the equipment required to sterilize aroom, that is the gas generating apparatus, the gas distribution system,the instrument-module, the dehumidifier and the aeration unit are allmanufactured such that they can readily be carried by a single person.

Reference is now made to a further form of apparatus in accordance withthe invention shown in FIG. 10. The apparatus is mounted on a mobiletrolley and comprises a gas generator 100. Air is drawn in through aHEPA filter 101 by a fan 102 and passed into a vaporizer 103. Inside thevaporizer the air is first heated by a heater (not shown) and thenpasses over an evaporation plate (also not shown) A pump 105 deliversliquid sanitant from a sanitant bottle 106 in the form of droplets ontothe evaporation plate from which it is flash evaporated.

The heated air carrying the sanitant vapor is passed to a distributionplenum 108 and exits to the room at high velocity through one or morenozzles 109.

Provision is made either to connect a number of optical typecondensation monitors 120 directly to the gas generator and hence to acontrol module 121 (see FIG. 11), or the monitors may be connecteddirectly to the control module. The optical condensation monitorsmeasure the layer of condensation as it builds up on a surface orsurfaces of the monitor.

Connecting condensation monitors to the gas generator has the advantageof reducing the number of connections to the control module, especiallywhen a number of gas generators are used.

The condensation monitors are placed around the room at the locationswhere the rate of condensation is the lowest.

A complete multiple installation is shown in FIG. 11, with three gasgenerators 100 each with eight condensation monitors 120. Also connectedto the control system is an aeration unit 122 used to remove the gas atthe end of the cycle and the dehumidifier 123. A separate instrumentmodule 124 is also shown which has additional instrumentation to measurethe gas concentration and the RH within the room. A singlecommunications cable connects 24 all of the components to the controlmodule.

The normal technique to establish if a decontamination process has beensuccessful is to place Biological Indicators (BIs), in those parts ofthe chamber where it is the most difficult to achieve a kill. It isoften undesirable or not permitted to place BIs in a room, but it isnecessary to know that deactivation to the required level has beenachieved.

To overcome this difficulty condensation monitors may be used toestablish that the mass and the rate of formation of condensate aresufficient to achieve deactivation of the microorganisms on thesurfaces. It has been well established that once the required conditionshave been achieved that the “D” value for the most resistant organismsis about two minutes.

Therefore an exposure of the organisms under the correct conditions fortwelve minutes will achieve a log 6 reduction in the count of viableorganisms.

Satisfactory decontamination will only be achieved in a room if asufficiently high rate of liquid sanitant vapor is delivered into theroom to provide an adequate rate of formation of condensation.

But to be assured that decontamination has been achieved it is necessaryto measure the condensation levels with time in multiple locations inthe room.

The data from the condensation monitors together with the informationfrom the other instruments in the room may then be used to establishthat a satisfactory deactivation cycle has been completed.

The condensation sensors may be used in one of two ways. The first is tomeasure and then control the level of condensation by adjusting theliquid evaporation rate and the second is simply to use the monitor as aswitch. When used as a switch it simply gives a signal when an adequateamount of condensation has formed and the process is then considered tobe complete or allowed to dwell in that state giving a sufficient periodduring which the organisms are killed. There is a further variation tothe “switch” method in which two sensors are used at each location setat different levels of condensation. The first indicates whencondensation has started and the second when the level of condensationis sufficient to have caused a satisfactory level. It may then benecessary to have a “dwell” period during which the kill occurs.

The condensation monitors of the above apparatus are optical deviceswhich measure the layer of condensation. An electronic device may beused instead that gives a switch signal when a known level ofcondensation has arrived. The switch level depends on the constructionof the sensor plate. Sensor plates are single use disposable items andhence are inexpensive. The plates plug into a box which may be placed ata remote location within the room.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. An apparatus for decontaminating an enclosed space comprising: meansfor providing a flow of heated air; means for delivering a liquiddecontaminant to the heated air to be evaporated into the heated air toproduce an air stream containing a vapor of the decontaminant fordelivery to a space to be decontaminated; and a self contained unitcomprising a duct to be positioned within the enclosed space having aninlet end and an outlet end, a fan for causing air to flow from theenclosed space through the duct, a filter for filtering air at the inletend of the duct, means for holding a supply of aqueous hydrogen peroxidesolution, means for delivering aqueous hydrogen peroxide solution fromthe means for holding to a heater to evaporate the aqueous hydrogenperoxide to produce hydrogen peroxide/water vapor which is entrained inthe air flow passing through the duct, and a nozzle at the outlet end ofthe duct, all internal and external surfaces of the apparatus open tothe enclosure being exposed to the hydrogen peroxide/water vaporcarrying air in the enclosure to decontaminate the surfaces.
 2. Theapparatus as claimed in claim 1, wherein the components of the apparatusare mounted to a support for transport of the apparatus.
 3. Theapparatus as claimed in claim 2, wherein the self-contained unit is amobile or portable unit for movement from location to location where itis to be used.
 4. The apparatus as claimed in claim 3, wherein thesupply of hydrogen peroxide/water vapor and/or the nozzle are readilyremovable for transport of the apparatus.
 5. The apparatus as claimed inclaim 1 further comprising a control box for controlling operation ofthe apparatus, wherein means are provided for delivering air causinghydrogen peroxide/water vapor from the atmosphere in the enclosurethrough the control box to decontaminate inner surfaces of the controlbox.
 6. The apparatus as claimed in claim 1 further comprising aseparate monitoring unit for monitoring the temperature of theatmosphere in the enclosure and the concentration of hydrogenperoxide/water vapor in the atmosphere, wherein means are provided fordelivering a flow of air carrying hydrogen peroxide/water vapor throughthe enclosure of the monitoring unit to decontaminate interior surfacesof the monitoring unit.
 7. The apparatus as claimed in claim 1 furthercomprising means for rotating the nozzle universally to deliver hydrogenperoxide/water vapor throughout the enclosure.
 8. The apparatus asclaimed in claim 1 further comprising means for continuously rotatingthe nozzle while the hydrogen peroxide/water vapor is dispersedtherethrough.
 9. An apparatus for decontaminating a space comprising: anelongated duct having a first end with an inlet opening formed thereatfor receiving air from the environment surrounding the duct and havingan opposing second end with a nozzle formed thereat for dispensing theair within the duct into the environment surrounding the duct; a fancoupled with the duct, the fan being configured to draw air from theenvironment into the duct through the inlet opening and to blow the airout of the duct through the nozzle into the environment; a heatercoupled with the duct, the heater being configured to heat the airtraveling through the duct; a container housing a supply of an aqueoushydrogen peroxide solution; an evaporator coupled with the ductdownstream of the heater so that the heated air passes through theevaporator, the evaporator also being in fluid communication with thecontainer so that when the aqueous hydrogen peroxide solution isdelivered from the container to the evaporator, the aqueous hydrogenperoxide solution is evaporated by the evaporator to produce a hydrogenperoxide/water vapor that is entrained into the heated air flowingthrough the duct; and a pump configured to deliver the aqueous hydrogenperoxide solution from the container to the evaporator.
 10. Theapparatus for decontaminating a space as recited in claim 9, furthercomprising a support frame that supports the duct.
 11. The apparatus fordecontaminating a space as recited in claim 9, wherein the nozzle isfreely exposed at the second end of the duct so that the air having thehydrogen peroxide/water vapor entrained therein can be dispensedtherefrom into the environment surrounding the duct.
 12. The apparatusfor decontaminating a space as recited in claim 9, further comprisingmeans for continuously rotating the nozzle while the air having thehydrogen peroxide/water vapor entrained therein is dispensed therefrom.13. The apparatus for decontaminating a space as recited in claim 9,wherein the duct, fan, heater, container, evaporator and pump from amanually transportable unit.
 14. The apparatus for decontaminating aspace as recited in claim 9, wherein the evaporator is configured toperform flash evaporation of the aqueous hydrogen peroxide solution.